SMAD2 and pulmonary fibrosis: Although there is no direct evidence that GRP stimulates TGF-β signalling pathway, Zhou and colleagues showed that the radiation induced fibrosis by increasing the number of p-Smad2/3 immunoreactive cells in the lungs of mice and the administration of GRP inhibitor regressed the pulmonary fibrosis by decreasing the number of p-Smad2/3 in the lungs [16].